Telescopic optical instruments commonly feature an actuator which is coupled to an erector system comprising lenses, a guide tube and a cam tube. By rotation of the cam tube inside the guide tube, the lenses are moved relative to each other thus increasing or decreasing the target image in magnification. By result, the user is able to see the target larger or smaller, but without any indication of selected power setting inside the field-of-view. The selected power setting is commonly indicated on an exterior portion of the actuator by means of magnification numbers. The user consequently must interrupt watching the target image and observe the actuators numbers while dialing-in a desired magnification factor. This becomes an even more critical disadvantage with optical instruments that combine the power changing function with other functions. Such other functions may be of opto-mechanical nature, for example, auto-compensation systems that feature reticles that are off-set from the optical axis. Other functions may be of electrical nature, for example, automatic switching on or off illumination systems for reticles when reaching a particular power setting. Consequently, some indication of the selected power setting and/or a resulting auto-compensation distance or similar power-setting dependent parameter inside the field-of-view is desired. Similar problems exist with non-firearm scopes, such as observation optics, spotting scopes and the like.
What is required is a system and method for making the selected power setting and related information visible to the user inside the field-of-view.